Chapter 23 VLAN Stacking

23.3 VLAN Tag Format

A VLAN tag (service provider VLAN stacking or customer IEEE 802.1Q) consists of the following three fields.

Table 60 VLAN Tag Format

Type

Priority

VID

 

 

 

Type is a standard Ethernet type code identifying the frame and indicates that whether the frame carries IEEE 802.1Q tag information. SP TPID (Service Provider Tag Protocol Identifier) is the service provider VLAN stacking tag type. Many vendors use 0x8100 or 0x9100.

TPID (Tag Protocol Identifier) is the customer IEEE 802.1Q tag.

•If the VLAN stacking port role is Access Port, then the Switch adds the SP TPID tag to all incoming frames on the service provider's edge devices (1 and 2 in the VLAN stacking example figure).

•If the VLAN stacking port role is Tunnel Port, then the Switch only adds the SP TPID tag to all incoming frames on the service provider's edge devices (1 and 2 in the VLAN stacking example figure) that have an SP TPID different to the one configured on the Switch. (If an incoming frame’s SP TPID is the same as the one configured on the Switch, then the Switch will not add the tag.)

Priority refers to the IEEE 802.1p standard that allows the service provider to prioritize traffic based on the class of service (CoS) the customer has paid for.

•On the Switch, configure priority level of the inner IEEE 802.1Q tag in the Port Setup screen.

•"0" is the lowest priority level and "7" is the highest.

VID is the VLAN ID. SP VID is the VID for the second (service provider’s) VLAN tag.

23.3.1 Frame Format

The frame format for an untagged Ethernet frame, a single-tagged 802.1Q frame (customer) and a “double-tagged” 802.1Q frame (service provider) is shown next.

Configure the fields as highlighted in the Switch VLAN Stacking screen.

Table 61 Single and Double Tagged 802.11Q Frame Format

 

 

 

 

 

 

DA

SA

Len/

Data

FCS

Untagged

 

 

 

 

 

 

 

 

Etype

 

 

Ethernet

 

 

 

 

 

 

 

 

 

 

 

frame

 

 

 

DA

SA

TPI

Priorit

VID

Len/

Data

FCS

IEEE 802.1Q

 

 

 

 

 

D

y

 

Etype

 

 

customer

 

 

 

 

 

 

 

 

 

 

 

tagged frame

DA

SA

SPTPI

Priorit

VI

TPI

Priorit

VID

Len/

Data

FCS

Double-tagged

 

 

D

y

D

D

y

 

Etype

 

 

frame

 

 

 

 

 

 

 

 

 

 

 

 

Table 62

802.1Q Frame

 

 

DA

 

Destination Address

Priority

802.1p Priority

 

 

 

 

 

SA

 

Source Address

Len/Etype

Length and type of Ethernet frame

 

 

 

 

 

(SP)TPID

 

(Service Provider) Tag Protocol IDentifier

Data

Frame data

 

 

 

 

 

VID

 

VLAN ID

FCS

Frame Check Sequence

 

 

 

 

 

182

 

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